The present invention relates to the swivel joints, and more particularly to a multi-directional hydraulic swivel joint which has an improved structure for permitting the swiveling of the joint thereof across a substantial range of angles in multiple directions and which has been characterized in automatic positioning.
Prior art swivel joint most likely has a structure permitting swiveling the joint only in single direction. This can not satisfy a full testing of a specimen both in the tension and compression testing or broadly apply to a mechanical arm of an industrial robot. U.S. Pat. No. 4,318,572 discloses a Tension-compression swivel joint with hydraulic force reaction which permits a quite wide ranges of swiveling without friction problems, but which has the same disadvantage of directional limitation. The joint as disclosed only permits to swivel along a front and rear direction but can not swivel laterally. This limits the joint to perform dual directional swiveling function. According to the theory and actual experiments, it is understood that a single directional swivel joint is not sufficient to apply to a mechanical arm of an ordinary industrial robot and the grips of an universal testing machine or a tool mechine for their precise adjustment and positioning purpose. Up to now, insofar as it is aware, the art contains no indication of the desirability of providing a multi-directional swivel joint as disclosed in this invention which tends to solve the above recited problems in the domain of the specimen test.